Zinc (Zn) is a trace element contained in a high concentration next to iron throughout all the tissues and body fluids of human beings.
Physiological actions of zinc relate to, for example, growth, skeleton growth, activation of metabolism of skin and its related organs, maintenance of reproductive functions, maintenance of gustatory sensation and olfactory sensation, effects on mental conditions and action, improvement of immunological functions, etc.
Enteropathic acrodermatitis syndrome known as a recessive hereditary disease, whose main symptom is a characteristic tetter, is obviously due to zinc deficiency. Furthermore, it is reported that in the long-term intravenous zinc-deficient nutrition practice similar symptom to enteropathic acrodermatitis syndrome appears. Still furthermore, it is confirmed and reported that even in skin diseases showing common observations to those of enteropathic acrodermatitis syndrome, such as seborrheic dermatitis, psoriasis vulgaris, bullous dermatitis, pruritus cutaneus, etc. or even in case of injuries, burn injuries, frostbites, a blood zinc concentration is lowered, often resulting in zinc deficiency.
It is known, on the other hand, that when zinc is excessively taken in, there occur diarrhea, stomach erosion, decrease in plasma HDL cholesterol, etc. and in serious cases there occurs dehydration.
Fatty acids having 16 to 22 carbon atoms and at least two double bonds such as linoleic acid, .gamma.-linolenic acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (Ara), dihomo-.gamma.-linolenic acid (DGLA), etc. are called generally multivalent unsaturated fatty acids, and constitute cell membranes as major components and furthermore take part in control of membrane fluidity, etc. Still furthermore, they have an antilipotropic action, an antiinflammatory action and an antithrombotic action. Still furthermore, they are important precursors for prostaglandins (PG) having functions to control an immunological system, a circulatory system, a hormone secretory system, etc.
There are many reports that linoleic acid has an action to retain water in the skin and effects on prevention of adult diseases caused by excessive intake of animal fat containing a large amount of saturated fatty acids as one factor, such as an action to lower a blood cholesterol concentration, an anti-cancer action, etc.
It is reported that .gamma.-linolenic acid has a stronger action to lower a blood cholesterol concentration than linoleic acid, an anti-allergic action, an effect on atopic dermatitis, control of fatty liver due to alcohol intake, relief of menstruation pain, etc.
It is reported that EPA has many physiological functions such as an antithrombotic action, an antilipotropic action, a hypotensive action, an antiinflammatory action, an anti-allergic action, etc.
It is reported that DHA has physiological actions on the cranial nerve system such as an action to improve the visual acuity reduction, an effect on improvement of memory and learning ability, an essential component of mother's milk for brain growth, etc.
It is reported that Ara has physiological actions such as an action as an essential fatty acid, an action to suppress skin psoriasis, an action to protect the stomach wall, an action to lower a blood cholesterol concentration, a liver-protecting action such as prevention of fatty liver, etc., an important substance for growth of fetal bodies or brains, etc.
It is reported that DGLA has similar physiological actions to those of .gamma.-linolenic acid and further has an action as a PG1 group precursor and such physiological actions as an anti-thrombotic action, a hypotensive action, an anti-dyskinesia action, etc.